I have been into collecting since childhood.
My Avatar is a pic of my favorite figure in a toy soldier collection that I started when about 10 years old. I used to spend all my paper-route money on these nice figures from england. My Mom once suggested I buy a football or Basketball etc, but I told her that these would be valuable one day as collecter items, so that it was kind of investing. It was nice that she would later see me start a side home business selling figures. One type I had and could get for about $1 back then sells for over $100 now. Most don't appreciate in value like that of course.
I totally get the card sorting enjoyment, and look for that sort of thing to do as a relaxing past-time. I only collect one kind of card, which is any Lion-King themed cards (or collectible stickers). You would not believe how many different kinds have been and continue to be made. It is never ending, and especially fun trying to track down obscure foriegn cards and series. The Lion King is such a popular subject worldwide. This collection started unintentially with a visit to Burger King with my then small daughter. We were trying to get the Lion King figures, but they ran out and were giving out packs of Lion King Cards instead. I was looking for things to collect with her and decided to try it. She is not really interested in the subject anymore (its all writing, anime, cosplay) but I continue the collection anyway and still show her my latest aquistions.
I also have a very large collection of LOTR figures, the 2 1/2 inch size. Its about at 1100-1200 figures now. I buy and sell a lot of those as part of my home business and all the damaged or incomplete ones are added to my collection to swell the ranks. I make and sculpt my own figures as well and can easily repair, convert or make new weapons, etc.
The two most enjoyable aspects for me are the sorting/organizing, and visual pleasure of setting up scenes of favorite subjects. When my son was young, he would help by fighting battles with the guys I set up, thereby knocking them down again. This gave me the chance to make a new set up, so it was a very symbiotic relationship.